Manuscript under review for Psychological Science Body specific representations of action word meanings Journal Psychological Science r Fo Manuscript ID Manuscript Type Date Submitted by the Author Keywords Short report 24 Nov 2007 Re Complete List of Authors PSCI 07 1400 Casasanto Daniel Stanford University Psychology Cognition s Language Memory Motor Processes Handedness ew vi ly On Casasanto D In Review Body specific representations of action word meanings Psychological Science Running head Body specific word meanings Body specific representations of action word meanings Daniel Casasanto Department of Psychology Stanford University Under Review Please do not quote Daniel Casasanto casasanto alum mit edu Department of Psychology Jordan Hall Bldg 420 Stanford University Stanford CA 94305 Phone 650 353 1700 2 A human mirror neuron system responsible in part for both the perception and performance of actions has been posited to subserve the meanings of action words Processing words for actions performed with the legs e g kick or the hands e g pick produces somatotopic activation in sensorimotor cortices Aziz Zadeh Wilson Rizzolatti Iacoboni 2006 Hauk Johnsrude Pulvermuller 2004 Tettamanti et al 2005 and modulates motorevoked potentials recorded from associated effector muscles Buccino et al 2005 The present study used the processing of manual action words in right and left handers as a testbed for the Body Specificity Hypothesis if concepts and word meanings are constituted in part by mental simulations of our own perceptions and actions then their neurocognitive representations should differ for people with different kinds of bodies who perceive and act upon the environment in systematically different ways Mirror neurons appear to be distributed bilaterally viewing a right or left hand in action tends to elicit activity in motor areas contralateral to that hand Aziz Zadeh et al 2006 Yet across studies activity in sensorimotor cortex associated with words for manual actions has been consistently lateralized to the left hemisphere This lateralization could be due to the general left hemisphere dominance for language Alternatively it could be a consequence of testing only right handed participants For stimulus words that name actions performed with the dominant hand i e the right hand the finding of leftlateralized motor activity suggests that understanding manual action words involves mentally simulating actions using mirror neurons contralateral to the hand that usually executes them This mental simulation claim would be challenged if the meanings of manual action words were found to be lateralized to the left hemisphere in left handers as well as right handers By contrast the simulation claim would be strongly supported if the motoric components of action word meanings were found to be lateralized differently in right vs left handers despite the fact that language function overall is left lateralized in the majority of both right and left handers Goodglass Quadfasel 1954 Methods Sixteen right handers and sixteen left handers according to the Edinburgh inventory Oldfield 1971 were recruited from Stanford University s introductory psychology class and were videotaped while performing a speeded motor meaning congruity task followed by a surprise recognition memory test 96 single words appeared in the center of a computer 3 screen one at a time for 2 seconds each Half were verbs naming manual actions e g paint chop draw that raters indicated they typically perform with their dominant hands and the other half were verbs naming non manual actions e g sigh peek giggle matched for length frequency and number of phonemes Half of the words appeared in red letters and the other half in blue letters A red box was placed on the left of the screen and a blue box on the right or vice versa and a white box filled with hundreds of clear glass marbles was placed above the screen in the middle As soon as each word appeared participants moved one marble into the box that matched the color of the letters For one block of 48 words participants used their left hand and for the other block their right hand Each block contained equal numbers of red and blue words and equal numbers of manual and nonmanual action words randomly intermixed The assignment of colors to words the positions of the red and blue boxes and the sequence of the left and right hand blocks were counterbalanced across subjects After completing the marble moving task participants performed an old new recognition memory test in which all of the words presented previously in red or blue were shown again in black letters randomly intermixed with an equal number of matched new words Participants were not instructed to imagine the actions that stimuli named or even to read the words but it was expected that they would read and understand the words incidentally If the meanings of action words are constituted in part by mental simulations of perceptuo motor experiences then a there should be effects of congruity between manual motor actions and the meanings of manual action verbs but not nonmanual action verbs and b right and left handed participants should show opposite effects of using their right and left hands to move marbles during incidental processing of manual action verbs Results Right handers were dramatically faster to initiate marble movements to the correctly colored boxes when using their right hands and left handers when using their left hands but only for manual action verbs fig 1a b 2 way mixed ANOVA showed a significant interaction of Handedness left hander right hander and Response Hand left hand right hand with no main effects F1 1 30 320 12 p 0001 F2 1 94 310 38 p 0001 By contrast no effects of handedness or response hand were found for non manual action verbs F1 1 30 1 F2 1 94 1 The 3 way interaction of Handedness Response Hand 4 and Verb Type manual non manual confirmed that the advantage of using the dominant hand to move marbles was found selectively for manual action verbs F1 1 30 320 63 p 0001 F2 1 94 306 01 p 0001 The magnitude of the response time congruity effect depended on participants degree of handedness The absolute value of participants laterality quotients Oldfield 1971 correlated reliably with their response time advantage RT non dominant hand RT dominant hand for manual action words r2 36 t 30 4 11 p 0002 but not for nonmanual action words r2 07 t 30 1 48 ns Right handers were also much more likely to